Angiogenesis, the process of new blood vessel formation from pre-existing capillaries, is very tightly regulated and normally does not occur except during embryonic development and reparative processes in the adult. However, dysregulation of angiogenesis is associated with pathogenesis many diseases including retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration. This is generally accomplished by down-regulation of negative and up-regulation of positive regulators of angiogenesis. Therefore, a better understanding of the regulatory processes that govern normal angiogenesis is key to understanding how abnormal angiogenesis occurs during disease. The recent discovery of specific cytochrome P450 expression (CYPs) in the vascular smooth muscle cells and endothelial cells (EC), and their contribution to vascular function suggest critical roles for these genes in vascular homeostasis. We recently showed that CYP1B1 plays an essential role in retinal vascular development and neovascularization during oxygen induced ischemic retinopathy (OIR). CYP1B1 deficient mice exhibited reduced retinal vascular density and failed to elicit a neovascular response during OIR. We also showed retinal EC prepared from CYP1B1-/- mice are less migratory and fail to undergo capillary morphogenesis in Matrigel. These cells also expressed significant amounts of an endogenous inhibitor of angiogenesis, thrombospondin-2 (TSP2), a gene shown to be up-regulated in response to oxidative stress. My hypothesis is that the increased oxidative stress in the absence of CYP1B1 results in sustained NF-:B activation and promotes increased production of TSP2. In Aim 1, we will determine the expression patterns of NF-:B and TSP2 during postnatal retinal vascular development and neovascularization during OIR using NF-:B-GFP/luciferase and TSP2-GFP transgenic mice. We will investigate whether NF-:B and TSP2 expression are altered in the absence of CYP1B1. In Aim 2, we will determine whether sustained activation of NF-:B in wild type retinal EC in vitro is sufficient to recapitulate the CYP1B1 null phenotype, attenuation of retinal EC adhesion, migration and capillary morphogenesis, and induce TSP2 expression. Understanding how CYP1B1 expression regulates retinal EC phenotype will provide new insight into novel mechanisms that regulate angiogenesis and aid in the development of more effective treatments. PUBLIC HEALTH RELEVANCE: Angiogenesis, the formation of new blood vessels from preexisting capillaries, occurs during development and in many reparative processes in adults, such as wound healing. Dysregulation of this process is associated with pathogenesis of a number of diseases including retinopathy of prematurity, diabetic retinopathy, and age-related macular degeneration, the major causes of blindness. A better understanding of how angiogenesis is regulated will aid in development of new and more effective therapies for these blinding diseases, as well as other diseases with a neovascular component.